Sheath device for inserting a catheter

ABSTRACT

A sheath device for inserting a catheter into a patient&#39;s body is described. The device has a first sheath with a proximal end and a distal end. When the device is used as intended, the distal end of the first sheath is provided for arrangement in the patient&#39;s body and the proximal end of the first sheath is provided for arrangement outside the patient&#39;s body. The first sheath comprises a tubular section and a sheath housing, which is disposed at the proximal end of the section and has a receiving channel for a strand-shaped body. The device solves the problem of reliably fixing a second sheath or a catheter with respect to the first sheath by providing a clamping element on the receiving channel for fixing a strand-shaped body in the receiving channel by way of clamping.

The invention resides in the mechanical field, and more particularly inthe medical engineering field, and relates to a sheath device forinserting a catheter into a patient's body.

Especially in microinvasive or minimally invasive applications in themedical field, functional elements such as stents, milling heads forclearing blood vessels by milling, or cardiac support pumps, arefrequently inserted into the interior of a patient's body, specificallyinto endogenous vessels, and more particularly blood vessels, through anopening by means of catheters. So as to be able to insert such cathetersonce or several times while minimizing the traumatization of theaffected tissue, and also while minimizing the risk of damage to thesensitive medical devices, sheaths are frequently employed, which arepermanently or temporarily introduced in a patient's body and which havean inner lumen, which allows a catheter or other functional elements tobe guided through. The Seldinger Technique, which will be described inmore detail below in connection with FIG. 1, is known for inserting sucha sheath into the patient's body.

A corresponding method is known from WO 02/43791 A1, for example.

Once such a sheath is installed, it can be used permanently orrepeatedly for inserting and removing a catheter.

A special application lies in the use of such a sheath for compressibleblood pumps or other functional elements, which are first compressed,notably radially compressed, so as to allow better introduction into thebody, and then inserted in the compressed state through the sheath tothe site of use or to the vicinity of the site of use, whereupon theyare expanded. For this purpose, corresponding blood pumps are known,which comprise a pump head at the distal end of a hollow catheter,wherein the pump head comprises a rotor having radially expandabledelivery blades and a likewise compressible and expandable housing. Thecorresponding elements are designed so that they expand automatically,for example if they have been previously elastically compressed, or thatthey are expanded at the start of a rotary operation by the resistanceof the liquid to be delivered, such as the blood (this applies inparticular to delivery blades of the rotor).

Other effects, such as shape memory effects in what are known as shapememory alloys, such as nitinol, can, for example, also be used for thepurpose of a subsequent shape change.

Corresponding compressible blood pumps are known from WO 02/43791 A1 orfrom EP 2 047 872 A1, and from DE 100 59 714, for example.

To allow better introduction, such blood pumps or other functionalelement can advantageously be precompressed by means of anaforementioned sheath and can be kept available, for example in a secondsheath, for the treatment of a patient before insertion into the firstsheath. The second sheath is then designed such that the functionalelement, notably the pump head, is held in a compressed state in theinterior of the sheath (lumen), for example in the same diameter whichis also required for insertion into the first sheath, or slightlylarger. So as to transfer the pump from the second sheath into the firstsheath, the two sheaths are then typically coupled such that they arecoupled coaxially relative to each other at the smallest possibledistance from each other, so as to axially displace the pump out of thesecond sheath and into the first sheath.

This procedure is critical because all components, and the catheter, thepump head and the second sheath in particular, are subjected to highmechanical stress. In addition, it is a problem that under surgeryconditions this sheath process must generally be carried out manuallyusing few other aids, placing high demands on the simplicity of theprocess and on the reliability.

Against this background, it is the object of the present invention tocreate a sheath device of the type mentioned above, which allows afunctional element to be inserted into the patient's body with highreliability, low sensitivity, low design complexity and low risk ofinjury to the patient and damage to the medical devices.

The object is achieved by the features of the invention according toclaims 1 and 10 and by a method according to claim 12.

According to the invention, a sheath device for inserting a catheterinto a patient's body is created, comprising a first sheath, theproximal end of which is provided for arrangement outside the patient'sbody when used as intended, while the distal end of the first sheath islocated inside the patient's body during use. The first sheath comprisesa tubular section and a sheath housing, which is disposed at theproximal end of the section and has a receiving channel for astrand-shaped body, and more particularly for a catheter and/or a secondsheath.

By providing a clamping element on the receiving channel, thestrand-shaped body, and more particularly the catheter and/or a sheath,can be clamped into the receiving channel. When a functional element,notably a pump, is precompressed at the end of a catheter in a secondsheath, this second sheath can be inserted into the sheath housing andfixed there by means of the clamping element. The second sheath and thefirst sheath can thus be oriented coaxially relative to one another andaxially fixed with respect to one another at a desired relativedistance, so that the catheter, together with the functional element,can be pushed from the second sheath into the first sheath.

The wall thickness and the material of the second sheath are selectedsuch that the second sheath can be clamped into the clamping elementwithout the catheter also being clamped in the second sheath. The designof the second sheath is so stable that it is compressed onlyinsignificantly during clamping. The wall thickness of thehollow-cylindrical second sheath can advantageously range between 0.2and 1.0 mm, and more particularly between 0.3 and 0.7 mm.

This also creates the option of removing the second sheath after theclamping element has been released, following the insertion of thecatheter and/or the functional element into the first sheath, and ofdesigning it as a peel-away sheath, for example, so that it can beremoved by tearing it open, with the catheter remaining in the receivingchannel. Despite the smaller diameter, the catheter can be clamped inthe clamping element so as to fix the functional element in thepatient's body with respect to the first sheath. A certain time afterinsertion, after the mechanical parts have settled and taken on thepatient's body temperature, readjustment may be necessary, and theclamping element can be released again, the catheter can be readjustedand the clamping element can be re-fixed. As an alternative, it is alsopossible to fix the catheter in a further clamping element which ismatched to the smaller diameter.

According to an advantageous embodiment of the invention, the clampingelement comprises an elastically radially deformable clamping ring. Sucha radially deformable clamping ring is a very simple and cost-effectiveway of creating a clamping element which allows reliable clamping,without the risk of damaging a second sheath or a catheter. The clampingring can advantageously be produced from an elastomer and the volumethereof can be incompressible, so that it radially expands during axialcompression. However, it can also be composed of a foamed material, inwhich some of the volume can be compressed, but which likewise radiallyexpands during axial compression.

In addition, it is possible for the clamping ring to be produced from aplastic material or metal and to be slotted. Such a clamping ring can,for example, have a conical shape on the outside, so as to be radiallycompressible by the axial movement of a further ring designed as aclamping cone.

The invention can advantageously be such that the clamping ring can beexpanded radially inward by means of a screw element acting axiallyrelative to the receiving channel. Under surgery conditions, such ascrew element can be used, for example by means of a screw wheel havinga diameter that can also be greater than that of the sheath housing, tocompress a clamping ring in a simple manner, and thus clamp the secondsheath or the catheter.

When using a pressure piece having a wedge-shaped cylindricalcross-section, the invention can be attained by radially inwardlycompressing the clamping ring by means of the axially acting screwelement and an axially movable wedge body, notably a ring having awedge-shaped cross-section.

So as to minimize the penetration of microbes into the patient's bodythrough the first sheath both when inserting a second sheath and acatheter and later, during operation, it is further possible for aradial expansion of the receiving channel to be provided on the side ofthe clamping ring located opposite the pressure piece or wedge body, asseen looking in the axial direction, the radial expansion comprising aflushing element.

For the same purpose, and additionally so as to prevent body fluids,notably blood, from exiting through the sheath, according to theinvention a valve sealing the receiving channel may be disposed in theflushing space, and more particularly on the side of the clamping ringlocated opposite the pressure piece or the wedge body, as seen lookingin the axial direction. Such a valve can, for example, be designed as adual valve comprising a plate valve and a dome valve, wherein the platevalve provides optimal sealing action if no catheter and/or no secondsheath extends through the receiving channel, whereby the plate valve asa whole can be held in a closed state. If a catheter or anotherstrand-shaped body is pushed through, the dome valve, which can, forexample, take on the geometric shape of a spherical cap, allows optimalsealing around the strand-shaped body. However, different designs of thevalve are also possible to fulfill the aforementioned sealing functions.

In addition to a sheath device of the type mentioned above, theinvention further relates to a catheter device comprising acorresponding sheath device and comprising a catheter, which extendsthrough the receiving channel and is fixed in the clamping element.

The invention further relates to a catheter device comprising a sheathdevice, as that which is described above, and a catheter and furthercomprising a second sleeve-shaped sheath, which surrounds the catheterand extends through the receiving channel, the sleeve-shaped secondsheath being fixed in the clamping element.

In addition to a sheath device and a catheter device of the typesdescribed above, the invention also relates to a method for inserting acatheter into a patient's body by means of a sheath device according toany one of the variants described above and comprising a second sheath,wherein the second sheath is first inserted together with the catheterinto the first sheath, and more particularly to a mechanical stop, andwherein the second sheath is thereafter fixed by means of the clampingelement and the catheter is then transferred from the second sheath intothe first sheath.

According to an advantageous embodiment of the method according to theinvention, the second sheath is removed, in particular by tearing itopen or off, after the catheter has been inserted into the first sheath.

The method according to the invention can advantageously provide for thecatheter to be directly fixed in the clamping element after the secondsheath has been removed.

The invention will be shown in drawings and then described hereafterbased on an exemplary embodiment. In the drawings:

FIG. 1 is a schematic overview of a vascular system comprising aninserted first sheath;

FIG. 2 is a detailed view of a section of FIG. 1;

FIG. 3 shows an embodiment of the invention comprising a first sheathand a second sheath;

FIG. 4 shows an embodiment of a pump;

FIG. 5 shows a second sheath comprising a pump extracted therefrom;

FIGS. 6, 7 show the pulling of a pump into a second sheath;

FIGS. 8, 9 show the transfer of a pump from a second sheath into a firstsheath;

FIG. 10 is a longitudinal section through a sheath housing comprising atubular section;

FIG. 11 is a longitudinal section through a portion of a sheath housingcomprising a cutting element;

FIG. 12 is a longitudinal section through a sheath housing comprising aclamping element for the tubular section and a further clamping element;

FIG. 13 is a longitudinal section through an alternative clamping ringcomprising a conical pressure piece; and

FIG. 14 is a longitudinal section through a sheath housing comprising aclamping element for a proximally introduced strand-shaped body.

FIG. 1 shows a schematic human vascular system 1. One of the femoralarteries 2 is located in the groin region and is connected to the aorticarch 3 via an aorta and then leads into the ventricle 4. An introducersheath 10 is first inserted into the femoral artery 2, for example usingthe Seldinger Technique. The femoral artery, or any blood vessel, ispunctured for this purpose, for example using a steel cannula having acutting tip. A guide wire 12 is pushed through the steel cannula, whichis inserted into the puncture site, and inserted into the left ventricle4 retrogradely via the aortic arch 3. After the puncturing cannula isremoved, the first sheath 10, which is designed as an introducer sheathand comprises a tubular section 11 and optionally a dilator, which isnot shown here, is threaded on the guide wire and inserted into thevascular system through the punctured site, wherein the sheath isinserted a short distance into the lumen of the vascular system or evento the site of use of an element to be inserted. Thereafter, a fluidpump is inserted into the vascular system through the introducer sheath10.

The tubular section 11 of the first sheath 10 is inserted into theartery such that the proximal end of the first sheath 10 is locatedoutside the femoral artery and can thus be used for inserting a pump,for example. It is thus possible to thread the pump on the guide wire 12so as to guide the pump into the left ventricle by means of the guidewire.

It is also possible to guide the tubular section 11 of the first sheath10 through the guide wire into the left ventricle and to then remove theguide wire 12 from the first sheath. A pump unit that may be present isthen guided through the first sheath volume into the vicinity of or intothe left ventricle 4.

In the present example, the method is only illustrated based on theinsertion of a pump into the left ventricle so as support a cardiacfunction. However, it is easy to see for a person skilled in the artthat the pump, or another functional element, can also be disposed andintroduced in other regions of the endogenous vascular system.

FIG. 2 shows the region of FIG. 1 in which the first sheath 10 is guidedfrom outside through the endogenous tissue into the lumen L_(G) of thefemoral artery 2. The first sheath comprises a tubular section 11, whichis connected to a sheath housing 13 at the proximal end. The tubularsection 11 defines a lumen L₁, which has an inside diameter d₁₁. Thisinside diameter widens toward the proximal end of the tubular section 11in a trumpet-like shape in the region 14.

The sheath housing 13 contains a haemostatic valve, which is known fromthe prior art. This valve prevents fluid present in the lumen L_(G) fromexiting to the outside through the lumen L₁.

In the illustration of FIG. 3, the first sheath 10 of FIG. 2 is coupledto a second sheath 20. Only a tubular section 21, which defines a lumenL₂ having an inside diameter d₂₁, is shown of the second sheath 20. Theoutside diameter of the distal end of the second sheath 20 is such thatit can be inserted into the sheath housing 13. However, the insidediameter d₂₁ is larger than the inside diameter d₁₁.

A pump, which is not shown and present in the lumen L₂, can now betransferred into the first sheath lumen L₁ from the second sheath lumenL₂ by pressing. The pump is then transported through the first sheathlumen L₁ to the site in the vascular system where the pump is intendedto effect the action thereof. The pump can either be guided on a guidewire for this purpose, or it can be introduced without guide wirethrough the first sheath lumen. The first sheath can be advanceddistally to the site of use of the pump before the pump is pushed out,so as to protect the pump and the vascular walls as well as the shaftcatheter.

A possible embodiment of a pump 30 will be described in more detailbased on FIG. 4. The pump 30 comprises a distal pump unit 31 and a shaftcatheter 32, which adjoins the proximal end of the distal pump unit 31.At the proximal end, which is not shown, the shaft catheter 32 comprisesa coupling for coupling the shaft catheter 32 to a drive element. Thedrive element can be disposed outside the patient's body and causes aflexible shaft extending in the shaft catheter 32 to rotate, which inturn drives the distal pump unit 31.

The distal pump unit comprises a pump housing 33, which is produced fromintersecting nitinol struts. Portions of the nitinol housing areprovided with a coating 34, which extends distally and proximally of arotor 35 disposed in the housing 33. The rotor is connected to the shaft36 extending through the shaft catheter 32 and thus caused to rotate.The housing and the rotor can be compressed, which is to say the pump isa self-decompressible pump. The pump deploys after the distal pump unitis pushed out at the distal end of a sheath. So as to compress the pumpin preparation for the implantation, the distal pump unit is pulled intothe distal end of a sheath lumen of a second sheath. The inside diameterof the sheath lumen is at least greater than the outside diameter of theshaft catheter.

The rotor may be displaceable relative to the pump housing in the axialdirection, notably by means of an axial displacement of the drive shaft.However, the rotor may also be fixed in the axial direction relative tothe pump housing.

The pump optionally comprises an outflow hose 37, which defines a flowduct for the pumped fluid located proximally of the rotor 35. Dischargeopenings, which are not shown in detail, are located at the proximal endof the outflow hose 37.

The pump can, of course, also be switched from pumping operation tosuction operation, so that the pump no longer conducts fluid from thedistal end to the proximal end, but vice versa.

A detailed description of a further suitable pump can be found indocument EP 2 047 872 A1, for example.

The function of the system shall now be described based on FIGS. 5 to 9.

FIG. 5 shows a pump 30′, which substantially corresponds to the pump 30of FIG. 4. To simplify matters, details of the pump are not shown. Onlythe bellied housing and the “pigtail” located distal of the belliedhousing are shown, the pigtail preventing the heart pump from beingsuctioned against the cardiac wall. The shaft catheter 32′ runs proximalof the distal pump unit 31′. A second sheath 20′ is provided, whichencloses a region 38′ of the shaft catheter 32′ and comprises a lumenL₂, the inside diameter d₂, of which is smaller than the diameter of thedistal pump unit 31′ when it is deployed.

The pump 30′ shown in FIG. 5 is a compressible pump, which is to say thedistal pump unit 31′, which comprises the pump housing and the rotorlocated therein, among other things, is designed such that it can becompressed, which is to say that the diameter thereof can be decreased.After a quality inspector or a physician, for example, has confirmed thecorrect function of the pump 30′, such as by observing the rotationalmovement of the rotor unit located in the distal pump unit 31′ during atest run, the distal pump unit 31′ is pulled into the lumen L₂ of thesecond sheath 20′ by pulling the shaft catheter 32′ in the proximaldirection. By pulling the pump into the second sheath 20′, bending ordamage of the shaft catheter or of the shaft extending therein isprevented. The pump 30′ shown in FIG. 5 and the second sheath 20′enclosing the region 38′ of the shaft catheter 32′ form a system 200which allows the function of the pump 30′ to be tested in due timebefore surgery and the pump to be compressed by pulling the distal pumpunit 31′ into the distal end of the second sheath 20′, and thus preventdamage to the shaft.

Although the system can be implemented both with actively decompressiblepumps and with self-decompressible pumps, it is particularly suitablefor self-decompressible pumps, which is to say pumps in which the distalpump unit automatically restores the original size outside the sheath.

FIG. 6 shows an intermediate step when pulling the distal pump unit 30′into the lumen of the second sheath 20′. It is apparent that the distalpump unit 30′ can be compressed and reduced to a smaller diameter, sothat the distal pump unit 30′ can be accommodated in the lumen of thesecond sheath 20′.

FIG. 6 further shows a coupling 39′ adjoining the shaft catheter 32′,the coupling allowing the shaft extending in the shaft catheter to becoupled to a drive unit. Because the coupling 39′ often times has alarger outside diameter than the inside diameter of the lumen L₂, thesecond sheath 20′ is usually added from the proximal end of the shaftcatheter 32′ in the distal direction before the coupling 39′ is mounted,so that the pump is shipped as a system 200, which is to say the pumpcomprising the second sheath 20′ located proximal of the distal pumpunit 31′ and the sub-assembled coupling 39′. FIG. 6 also shows a slightexpansion of the distal end of the second sheath 20′. The trumpet-shapedexpansion 24′ makes it easier for the distal pump unit 31′ to be pulledinto the lumen L₂ of the second sheath 20′.

In FIG. 7 finally the distal pump unit 31′ is located entirely in thelumen L₂ of the second sheath 20″. The second sheath 20″ comprises twosub-assembled grip units 22″, which allow better holding or removal ofthe second sheath 20″ when pulling the distal pump unit 31′ into thelumen L₂, or subsequent tearing. If a “pigtail” is present, the same isadvantageously likewise pulled into the lumen L₂, so that the distalpump unit 31′, together with the components of the pump located distalof the distal pump unit 31′, are present in the lumen L₂.

It is apparent from FIG. 8 how the system 200 comprising the pump 30′and second sheath 20″ is combined in an operative connection with thefirst sheath 10 to form a system 100. First, the distal end of thesecond sheath 20″ is inserted into the sheath housing of the firstsheath 10. As soon as the distal tip of the second sheath 20″ is seatedagainst the mouth of the tubular section of the first sheath 10, thepump is transferred from the second sheath 20′ into the first sheath 10′by pushing the pump in the distal direction, the pushing taking place bypushing of the shaft catheter 32′. The diameter of the distal pump unit31′ is thus reduced further to the inside diameter d₁₁ of the lumen L₁.

FIG. 9 shows the subsequent step, in which the distal pump unit 31′ islocated entirely in the lumen L₁ of the first sheath 10. The fact thatthe distal pump unit 31′ is located entirely in the lumen L₁ of thefirst sheath 10 can be indicated, for example, by using a coloredmarking 50 which is applied to the outside of the shaft catheter 32′.

The second sheath 20″, which is designed as a “peel-away” sheath, isthen removed from the shaft catheter 32′ by tearing open the peel-awaysheath from the proximal end to the distal end and pulling it off theshaft catheter 32′. The directed tearing open from the proximal end tothe distal end can be supported by notches A, however it is primarilybased on the orientation of the molecule chains of the plastic materialthat is used from the proximal direction in the distal direction.

After the peel-away sheath has been removed, the pump 30′ is guidedfurther inside the lumen L₁ of the first sheath 10 to the desiredlocation.

The first sheath can optionally be advanced to the immediate vicinity ofthe site of use before or after the pump has been inserted using thedistal sheath mouth. The first sheath has the required length to do so.

A reinforcement of the second sheath 20″ is not required, in particularwhen pulling the distal pump unit 31′ into the distal end of the secondsheath lumen L₂, because the risk of the shaft kinking during a pullingmotion is significantly reduced.

When the pump is transferred from the second sheath to the first sheath,as shown based on FIGS. 7 to 9, the second sheath may comprise areinforcing structure in form of an introduced wire, or the tubularsection 21″ of the sheath 20″ is not produced from a flexible plasticmaterial, but from a non-deformable plastic material or metal.

Another option for stabilizing the pump and the second sheath is that ofholding the second sheath 20″ by way of a supporting element 40 in formof a stable outer sleeve when advancing the pump 30′ in the distaldirection, which is to say in particular when transferring the pump 30′from the second sheath into the first sheath.

Hereafter, another possible variant of a method for inserting a pumpinto a left ventricle shall be described. As a preparatory measure, thepump is first filled with a sterile physiological salt solution and isthus completely freed from air. Then, the peel-away sheath locatedproximal of the distal pump unit is advanced to a potentially presentoutflow hose. The diameter of the peel-away sheath is 10 Fr, forexample. After the peel-away sheath has been advanced to the outflowhose, the peel-away hose is surrounded by a sleeve-shaped element so asto hold the second sheath. The distal pump unit is then pulled into thepeel-away sheath, optionally by performing a slight rotational movement,by performing a pulling motion in the proximal direction on the shaftcatheter. The pump is advanced into the second sheath so far that apotentially present pigtail is likewise secured in the peel-away sheath.These steps make it possible to examine the functional capability of thepump even before surgery and to insert the pump only then into a sheath,without having to act under time pressure. For example, it is only thenthat the vascular system is punctured so as to insert the first sheath.However, so as to save time, it is thus also possible for an assistantto prepare the pump, while the user already carries out the puncturing.

After a 9 Fr introducer sheath, for example, has been introduced intothe left ventricle, a potentially present dilator is pulled out of theintroducer sheath and removed therefrom.

The pump, which is held in the peel-away sheath and which initially is,for example, enveloped by the sleeve so as to hold the second sheath, isthen pushed into the sheath housing until the tip of the peel-awaysheath strikes against a mechanical stop. The pump is then transferredfrom the peel-away sheath into the tubular section by pushing the shaftcatheter. As soon as the distal pump unit has been completelytransferred into the introducer sheath, as can be verified based on anoptical marking on the catheter shaft, for example, the peel-away sheathcan be torn open and pulled off the shaft catheter. The pump is thenadvanced inside the first sheath into the left ventricle. The firstsheath is subsequently pulled back out of the left ventricle, to thepoint where the descending aorta begins.

The positioning of the distal pump unit in the left ventricle can becontrolled by way of radioscopy, for example. For this purpose, an X-rayvisible marking is located on the pump housing or in the vicinitythereof, for example on the catheter, or the pump housing itself isvisible to X-rays. The discharge region of the pump, which is to say thedischarge openings of an outflow hose, should likewise be located in theregion of the ascending aorta. This can also be checked using an X-rayvisible marking. A potentially present pigtail catheter tip should makecontact with the tip of the left ventricle.

So as to remove the pump from the ventricle, the pump is retracted intothe introducer sheath by means of a pulling force that is applied to theshaft catheter and is removed from the arterial vascular system in thecompressed state. If the first sheath has already been shortened, thepump can also first be retracted a certain distance into the shaftcatheter so as to compress the pump. For this purpose, the shaftcatheter may comprise a pull-in funnel into which the pump can be pulledby pulling on the drive shaft. The first sheath and further remainingcomponents are then removed from the vascular system.

The invention provides a particular advantage when a long sheath is usedduring the implantation and explanation of the pump. The long sheath isnot only used, as is customary in the prior art, to insert the pump intoan endogenous lumen, but also to guide the pump through the sheath lumeninto the vicinity of the site of action. To this end it is advantageousin the medical field if the sheath has a length between 40 and 120 cm.The length is determined by the later site of action of the pump and thepatients physique.

If the pump is pulled out of the endogenous lumen together with the longsheath, bleeding of the femoral artery is stopped by means of a pressuredressing. As an alternative, the pump can be pulled out of the sheathlumen of the long sheath. A further guide wire can then be placedthrough the lumen of the sheath, and an element for closing the puncturecan be guided via this guide wire after the sheath has been removed.This allows improved stemming of the bleeding to be achieved.

FIGS. 10 to 13 show in particular an embodiment of the first sheathaccording to the invention, comprising one or more clamping elements forfixing a tubular section 41 in a sheath housing 43.

FIG. 10 shows a longitudinal section of a sheath housing 43, whichsubstantially has the shape of a cylindrical sleeve which is closed atleast at the distal end 44 facing the patient's body by a pressure screw45. The sheath housing 43 has a continuous receiving channel 46 for atubular section 41 of the first sheath. In the illustration of FIG. 10,coming from the patient's body, the tubular section 41 is showncontinuously up to the flushing space 47 of the receiving channel 46,and then in dotted form in the proximal direction. This indicates thatthe tubular section 41 can be axially displaced relative to the sheathhousing 43 inside the receiving channel 46 or, in other words, thesheath housing 43 can be displaced on the tubular section 41.

So as to insert a functional element, for example a pump, into the firstsheath, the tubular section 41 is usually pulled out of the sheathhousing 43 in the distal direction so far, or it is positioned duringproduction of the first sheath, so that it ends approximately at thelevel of the first stop piece 48. A second sheath comprising a retractedpump, as described above, can be advanced up to this point, so as tothen move the pump from the second sheath into the first sheath.

The first clamping element comprises elements such as the first pressurescrew 45, a first clamping ring 50 made of an elastomeric material, andthe first stop piece 48.

The pressure screw is screwed to the sheath housing by means of anexternal thread in an overlapping region with the distal end 44 of thesheath housing 43. Manually rotating the pressure screw 45 thus bringsabout a movement of the pressure screw in the axial direction, whichresults in axial compression or expansion of the clamping ring 50.During an axial compression, the clamping ring 50 tends to give wayradially inward and outward so as to maintain the volume thereof andthus clamps the tubular section 41, because it experiences resistance atthe proximal side by the first stop piece 48.

The tubular section 41 is thus axially fixed with respect to the sheathhousing 43. This fixation can easily be released by loosening thepressure screw 45, so that the tubular section 41 is then easy toaxially displace in the sheath housing 43. To this end, when it isrelaxed, the clamping ring can have an inside diameter that equal to orlarger than the diameter of the first sheath.

So if the tubular section 41 is first pushed as far as possible into thepatient's body to allow insertion of the pump, protected by the sheath,to the site of use, for example a ventricle, the tubular section 41 ispulled out after the pump has been removed and the sheath as a wholeprotrudes relatively little from the patient's body. The clampingelement 48, 45, 50 can then be released and the sheath housing 43 can bepushed closer to the patient's body on the tubular section 41. Thetubular section 41 then extends completely through the sheath housing 43and optionally protrudes from the same in the proximal direction. Usingmeans which will be described in more detail hereafter, the tubularsection 41 can then be severed in some regions so as to remove theexcess length.

A so-called combined haemostatic valve, which is composed of a domevalve 51 and a valve plate 52, is provided inside the sheath housing 43to provide better sealing action. The valve plate closes the sheathhousing 43 if at this point neither the tubular section 41 nor a shaftcatheter extends through the receiving channel 46, while the dome valve51 is optimized so as to provide tight sealing around a strand-shapedbody, for example the tubular section or a catheter.

A further pressure screw 54 is provided at the proximal end 53 of thesheath housing 43, the pressure screw basically functioning in the samemanner as the first pressure screw 45 and effecting the compression of asecond clamping ring 56 relative to a second mechanical stop 57 via apressure piece 55. A special feature that should be mentioned here isthat the distal end of the second clamping ring 56 has a conical shape,which favors a deformation radially inward when exerting an axialpressure by way of the pressure screw 54. The second stop 57 has aconical design in the opposite direction. However, it is also possibleat this point to use a non-conical clamping ring 56, and instead onewhich has a rectangular or round cross-section.

FIG. 10 schematically indicates a flushing element 58, which allows theflushing space 47 to be flushed with a liquid that prevents microbesfrom penetrating into the patient's body through the first sheath. Thisflushing is particularly effective if the tubular section 41 ends in theflushing space 47 or on the distal side thereof, so that the flushingliquid can reach both the outside and the inside of the tubular section41.

FIG. 11 shows, by way of example, the arrangement and operatingprinciple of a cutting element according to the invention.

If no precut predetermined breaking points, or no predetermined breakingpoints that are predefined in another manner, for example by apredetermined molecule structure or regional weakening of the wallthickness of the tubular section 21, are provided, these can beintroduced in a suitable manner when using the first sheath by way of acutting element. In the region of the flushing space 47 of the sheathhousing 43 in FIG. 11, a cutting element comprising blades 59, 60 isprovided, which cuts the tubular section in the circumferential section,for example during a rotation of the sheath housing relative to thetubular section. It is also possible to introduce cuts in the axialdirection.

For this purpose, the blades 59, 60 can also be disposed such that theycut in the longitudinal direction during a movement of the tubularsection 41 in the axial direction, as indicated by the arrow 61. It ispossible to provide blades both for cutting in the circumferentialdirection and a blade for cutting in the longitudinal direction.

FIG. 11 also shows that the blades 59, 60 can be moved radially towardthe tubular section 41 by actuation from outside the sheath housing 43.There, a guide extending in the radial direction for one or more bladeholders, a corresponding seal and a suspension can be provided, so thatmicrobes are prevented from penetrating via this displacement elementfor the blades and the blades, when not actuated, radially have adistance from the tubular section 41. After use of the first sheath, itis then possible to manually apply pressure to the blades and theportion of the tubular section 41 that is not required can be cut off. Astop, which is not shown here, prevents the cutting depth from exceedinga critical dimension and causing damage to a catheter which may bepresent inside the sheath.

The blades shown can also form a cutting element for a second sheath.

FIG. 12 shows an advantageous use of the second clamping element on theproximal side of the sheath housing 43 after the tubular section 41 hasbeen shortened, and a shaft catheter 61 leads out of the proximal end ofthe tubular section 41 and then on to a coupling element, which is notshown, for a drivable shaft of a pump and out of the sheath housing 43.The shaft catheter is sealed in the aforementioned dome seal 51, and theclamping element, together with the elements of the second pressurescrew 54 and of the second clamping ring 56, which is axially compressedby the pressure piece 55 relative to the second stop 57, gives wayradially inward far enough for the shaft catheter 61, which has asubstantially smaller outside diameter than the tubular section 41 or asecond sheath, to be clamped and in particular to be additionallysealed. Both the tubular section 41 and the shaft catheter 61 protrudingtherefrom can thus be fixed in the sheath housing 43.

The second clamping element is likewise suitable for fixing the secondsheath with the second clamping ring 56, when inserting a second sheathinto the sheath housing 43, such that the second sheath is sufficientlyfixed with respect to the sheath housing 43, and notably with respect tothe tubular section 41, so as to allow the shaft catheter 61 to bepushed through.

The first and second clamping rings 50, 56 can be produced from anelastomer, for example a rubber or a silicone elastomer, and can thus befully elastic, but be deformable without being able to compress thevolume. At this point, using an elastic foamed material in which some ofthe volume can be compressed is also conceivable.

FIG. 13 is a schematic view of another type of a clamping ring 62, whichcan be produced from a plastic material or a metal, for example, and inparticular can be slotted and thus be radially compressible. The slottedclamping ring 62 has a conical outside contour, against which theconical contour of a pressure piece 63 pushes so as to radially compressthe clamping ring as soon as an axial pressure force is exerted on thepressure piece 63 in the direction of the arrow 65, for example by apressure screw shown above. The slotted clamping ring 62 is axiallyfixed by the stop piece 64.

FIG. 14 shows a sheath housing 43′ comprising in the interior thereof areceiving channel 46 for a sheath or a catheter. At the distal end 44,the sheath housing 43′ comprises a tubular section 41 which is attachedto this end and which can, for example, be glued or cast into an openingof the sheath housing or be attached therein in another manner. Thetubular section 41 is pushed into the opening of the sheath housing 43′up to a mechanical stop 63.

A second sheath 20′ is introduced into the receiving channel 46 from theproximal end 53 of the sheath housing 43′ so far that it ends distallyat the mechanical stop 63. In one embodiment, the system may also bedesigned so that the second sheath 20′″ ends directly at the tubularsection 41. For example, a functional element in the form of a pump,which is not shown, is pulled into the second sheath 20′″ with a hollowcatheter.

So as to transfer the catheter together with the pump from the secondsheath 20″' into the tubular section 41 of the first sheath 43′, 41, thetwo sheaths are oriented coaxially relative to one another inside thereceiving channel 46, and the second sheath 20′″ is fixed by means of aclamping element. The clamping element comprises an elastic clampingring 56′, which at the distal end has a conical design and is pressedagainst a mechanical stop 57′. For this purpose, axial pressure isexerted on the clamping ring 56′ by means of a pressure screw 54′, whichhas an external thread 64. To this end, the pressure screw 54′ isscrewed into the opening of the tubular portion of the sheath housing43′, so that the screw moves axially in the direction of the arrow 65.

The clamping ring 56′ is, for example, produced from an elastomer,expands in the radial direction under axial pressure and thus clamps astrand-shaped body located in the receiving channel 46. The secondsheath 20′″ has a wall thickness between 0.3 and 0.7 mm and is producedfrom a sufficiently stable material, so that the second sheath can beclamped under radial pressure, without the catheter extending thereinbeing clamped at the same time. The catheter can thus be easilydisplaced starting from the proximal end of the second sheath 20″' intothe tubular section 41. The second sheath 20′″ is sealed by a combinedplate and dome valve 51, 52 in a flushing space 47.

After the functional element, for example the pump, has been transferredwith the catheter from the second sheath 20′″ into the tubular section41, the second sheath can be torn open using the handles 67, 68 and beremoved. For this purpose, the second sheath comprises a preweakenedregion or notching along the axial direction, or an appropriatepredetermined molecule structure, which allows the second sheath to betorn open to the distal end thereof and to be removed accordingly. Forthe purpose of tearing the sheath open, it may be useful to release theclamping element 54′, 56′, 57′.

After the second sheath has been removed, the clamping element 54′, 56′,57′ can be clamped so far that the catheter, which has a smallerdiameter, is clamped in the receiving space 46 by the further radialcompression of the clamping ring 56′. The catheter, and thus a pump tobe implanted, is then fixed at the distal end of the catheter in theaxial direction with respect to the first sheath, and consequently withrespect to the patient body.

Moldings in the sheath housing, which are not shown here, implement arespective noticeable stop for the various end positions of the pressurescrew, which correspond to the various diameters to be clamped, and theuser thus feels a noticeably increasing rotational resistance whenactuating the screw when the respective clamping position is reached.

Following an initial phase, during which the arrangement settlesmechanically and heats up to the patient's body temperature, theclamping element can be released and the catheter can be readjusted andthen be re-fixed. In all areas where two cylindrical elements can besealingly nested inside one another in the aforedescribed construction,a conical seal having a cone angle of a few degrees can advantageouslybe used, as is known in principle in the medical field.

The described embodiment of a sheath allows an implantable heart pump,for example, to be transferred from a second sheath, in which the pumpis kept available following an initial inspection, into a first sheathleading into a patient's body without difficulty, low complexity andgreat reliability.

1-14. (canceled)
 15. A sheath device for inserting a catheter into apatient's body, comprising a first sheath having a proximal end and adistal end, the distal end of the first sheath being provided forarrangement in the patient's body when used as intended and the proximalend of the first sheath being provided for arrangement outside thepatient's body, and the first sheath comprising a tubular section and asheath housing, which is disposed at the proximal end of the section andcomprises a receiving channel for a strand-shaped body, wherein aclamping element for fixing the strand-shaped body in the receivingchannel by way of clamping is provided on the receiving channel.
 16. Thesheath device according to claim 15, wherein the clamping elementcomprises an elastically radially deformable clamping ring.
 17. Thesheath device according to claim 16, wherein the clamping ring isproduced from an elastomer.
 18. The sheath device according to claim 16,wherein the clamping ring is produced from a plastic material or metaland is slotted.
 19. The sheath device according to claim 16, wherein theclamping ring can be expanded in a radially inward direction by means ofa screw element acting axially relative to the receiving channel. 20.The sheath device according to claim 19, wherein the axially actingscrew element exerts axial pressure on the deformable clamping ring bymeans of a pressure piece.
 21. The sheath device according to claim 19,wherein the clamping ring is compressed radially inward by means of theaxially acting screw element and an axially movable wedge body.
 22. Thesheath device according to claim 21, wherein the wedge body is a ringhaving a wedge-shaped cross-section.
 23. The sheath device according toclaim 20 or 21, further comprising a radial expansion of the receivingchannel is provided on the side of the clamping ring located oppositethe pressure piece or wedge body, as seen looking in the axialdirection, the radial expansion comprising a flushing element.
 24. Thesheath device according to claim 20 or 21, further comprising a valvesealing the receiving channel is provided on the side of the clampingring located opposite the pressure piece or wedge body, as seen lookingin the axial direction.
 25. The sheath device according to claim 15,wherein the catheter extends through the receiving channel and is fixedin the clamping element.
 26. The sheath device according to claim 15,wherein the catheter extends through the receiving channel inside asecond, sleeve-shaped sheath, wherein the second sheath is fixed in theclamping element.
 27. A method for inserting a catheter into a patient'sbody, comprising: locating a distal end of a first sheath into apatient's body and maintaining a proximal end of the first sheathoutside of the patient's body; pulling a fluid pump into a second sheathresulting in a compression of the fluid pump; locating the second sheathwithin said proximal end of said first sheath; transferring the fluidpump in said second sheath to said first sheath; and fixing astrand-shaped body within a sheath housing connecting said first andsecond sheaths together with at least one clamping element.
 28. Themethod of claim 27, wherein said fluid pump is transferred by a pushingmotion of said strand shaped body attached to the pump.
 29. The methodof claim 28, wherein the second sheath is removed from the strand shapedbody after the fluid pump is transferred.
 30. The method of claim 27,wherein a first clamping element is located on said sheath housingdistal end and a second clamping element is located on said sheathhousing proximal end.
 31. The method of claim 30, wherein said firstclamping element selectively clamps said first distal end via a clampingring, a pressure screw and a first stop piece.
 32. The method of claim31, wherein rotation of the pressure screw moves it in the axialdirection to compress or expand the clamping ring depending on thedirection of axial movement.
 33. The method of claim 30, wherein saidsecond clamping element selectively clamps said second distal end via aclamping ring, a pressure screw and a second stop piece.
 34. The methodof claim 33, wherein rotation of the pressure screw moves it in theaxial direction to compress or expand the clamping ring depending on thedirection of axial movement.
 35. The method of claim 34, wherein adistal end of said clamping ring has a conical shape which favors adeformation radially inward when said pressure screw exerts an axialpressure.
 36. The method of claim 27, wherein the fluid pump is anexpandable, rotating pump.